1. Field of the Invention
The present invention relates to a multi-hop wireless communication system comprising a plurality of wireless stations.
2. Description of the Related Art
Multi-hop communication networks, in which packets are relayed from one station to another in a series of hops, are a technology that is currently gaining attention because it enables wireless stations to communicate without being within receiving range of each other's signals.
The medium access control (MAC) protocol described in Standard 802.11 of the Institute of Electrical and Electronics Engineers (IEEE) provides one method, known as Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA), of avoiding signal collisions in a wireless multi-hop communication network. This method, however, involves overhead that leads to communication delays, and employs a random back-off technique that leads to variations in delay time. These considerations limit the number of real-time connections (e.g., telephone calls) that the network can support simultaneously, as well as lowering throughput and quality of service (QoS).
A known way to reduce network delays and increase network throughput is to use multiple communication channels. Spreading the collision avoidance overhead over multiple channels can reduce the overhead in each channel to a level such that quality of service is not significantly impaired. In a proposed method of using multiple channels described in Japanese Patent Application Publication No. H10-290229, each wireless station has a wireless channel filtering section that enables a single transmitting and receiving module to support multiple simultaneously on-going connections on different channels by switching channels dynamically.
Besides requiring the additional wireless channel filtering section, however, this dynamic channel switching method generates switching overhead that also reduces throughput, increases communication delays, and limits the quality and quantity of service.